Wire conveyor belts are commonly used for conveying articles during coating, cooking, cooling, drying and other applications. The wire conveyor belts are often driven by sprockets similar to the sprocket 10 shown in FIG. 1.
When driving a belt in a breading or battering application, or any application in which material is added to the articles on the belt, it is common for excess material to accumulate on the support shelves, commonly called roots, 14 between the sprocket teeth 12. The material will build up on the support shelves 14. Once enough material has built up on the support shelves 14, the conveyor belt will be pushed so far away from the center 15 of the sprocket that it will no longer make adequate contact with the sprocket teeth 12 for effective driving. The conveyor belt will begin to skip as the sprocket teeth 12 move past the belt instead of engaging it and driving it forward.
With the applications where buildup of material is an issue, it has long been known that the width 17 of the sprocket has an effect. The narrower the sprockets used, the less of a problem the buildup will be, and, conversely, the wider the sprockets used, the more of a problem buildup will be. The material, whether crumbs, batter, or other materials, cannot build up easily on a narrow sprocket but can easily build up on a wide sprocket.
While narrow sprockets are best for fighting material buildup, there are two significant problems with using a narrow sprocket. First, the narrower the sprocket teeth 12 pushing on a conveyor belt are, the higher the force is in that small area to push the belt. Higher, more concentrated forces wear the conveyor belt faster. The best way to drive the conveyor belt is with as wide sprocket teeth 12 as possible.
Second, when using a narrow sprocket, there is no good means of attaching it to a drive shaft. The simplest and cheapest method of attaching a sprocket to a drive shaft is to use a set screw in a threaded hole 16 in the sprocket to hold it tightly against a drive shaft. However, it is difficult to fit such a set screw into an extremely narrow sprocket. As is shown in FIG. 2, a hub 18 may be used on the side of a sprocket 10. The threaded hole 16 for the set screw is then placed in the hub 18, but such a hub is then subject to the same experience of buildup of material as a wide sprocket.